The Science of Yoga: The Risks and the Rewards

by William J Broad

  The architects of the New York inquiry, as with most scientists who study humans, made sure its design included the imposition of controls meant to increase the likelihood that any observed changes were real rather than false clues or statistical flukes. Thus, the subjects in the metabolic chamber engaged sequentially in three different activities—reading a book, doing yoga, and walking on a treadmill. To provide a more detailed basis for comparison, the scientists had the subjects walk on the treadmill at different speeds. The imposed rates were two miles per hour and three miles per hour, the latter a fairly vigorous pace.

  The yoga was pure Ashtanga, the brisk, fluid style descended from Krishnamacharya. The workout began with twenty-eight minutes of Sun Salutations followed by some twenty minutes of standing poses such as the Triangle and Padahastasana, a forward bend in which the student grabs the feet and brings the head down to the knees. It ended with eight minutes of relaxation in the Lotus position and the Corpse pose. Overall, the yoga session lasted nearly an hour. Its strong focus on Sun Salutations made the routine one of the most vigorous to undergo careful examination.

  Hands to Feet, Padahastasana

  Despite the added zing, the scientists concluded that the yoga session failed to meet the minimal aerobic recommendations of the world’s health bodies. Its oxygen demands, they reported, “represent low levels of physical activity” similar to walking on the treadmill at a slow pace or taking a leisurely stroll.

  The only glimmer of cardiovascular hope centered, once again, on Sun Salutations. The New Yorkers found the oxygen challenge of the pose “significantly higher” than for the slow treadmill. A practice incorporating Sun Salutations for at least ten minutes, they wrote, may “improve cardio-respiratory fitness in unfit or sedentary individuals.” But the flip side, the scientists added, was that the posture offered few heart benefits for seasoned practitioners.

  Seeking a wide context, the scientists were careful to note that other research had demonstrated that yoga aided the body and mind in ways that extended far beyond athletics and aerobics. Hagins, the lead researcher, remarked in a university news release that the discipline had “positive health benefits on blood pressure, osteoporosis, stress and depression.” Yoga, he added, “may convey its primary benefits in ways unrelated to metabolic expenditure and increased heart rate.”

  That kind of prudence became the standard view in the world of science. Decades of uncertainty ended as a consensus emerged that yoga did much for the body and mind but little or nothing for aerobic conditioning. The California study receded as an anomaly, and the investigations in Texas, Wisconsin, and New York got cited repeatedly and respectfully in the scientific literature. Science and its social mechanisms had assessed a big claim and found it wanting.

  In 2010, a review paper documented the new accord. In the halls of science, the review article is a hallowed tradition because of its pithy generalizations. It gives a critical evaluation of the published work in a particular area of research and then draws conclusions about what is legitimate progress and what is not, what is good and what is bad. By definition, it weighs all the evidence. Given the rapid advance of science around the globe, as well as the soaring numbers of reports, such analyses are seen as increasingly important to upholding the standard of wide comprehension. Whole journals do nothing but publish review articles.

  The 2010 paper examined more than eighty studies that compared yoga and regular exercise. The analysis, by health specialists at the University of Maryland, found that yoga equaled or surpassed exercise in such things as improving balance, reducing fatigue, decreasing anxiety, cutting stress, lifting moods, improving sleep, reducing pain, lowering cholesterol, and more generally in raising the quality of life for yogis, both socially and on the job. The benefits were similar to those that had surprised the Duke team.

  In summary, the specialists reported that yoga excelled in dozens of examined areas.

  But the scientists also spoke of a conspicuous limitation for an activity that had long billed itself as a path to physical superiority. The authors noted that the benefits ran through all the categories—“except those involving physical fitness.”

  For the world of science, the issue seemed to be settled. But for the world at large? In truth, all the labors and analyses got little or no attention from the public, and most certainly not from yogis. The one exception was the Wisconsin study, which made a few waves. Overall, the rest of the studies sank without a ripple.

  The lack of public reaction was especially notable in the yogic community. In theory, it was the main beneficiary of the findings. Even so, no yoga book to my knowledge reviewed the developments or commented on the implications. No guru expounded on the details. Bikram Choudhury offered no barbed rejoinders. Yoga Journal fired off no more rebuttals. The disregard persisted even though the lead researchers in the Wisconsin and New York studies were themselves yogis who could be seen as sympathetic to the discipline.

  In the early days of modern yoga—in the era of Gune and Iyengar—science had been a role model. Influential gurus paid attention. No more. The affair was over.

  Some individuals and authors who did yoga—or who knew the diversity of modern athletics—seemed to understand the substance of the new findings. But they tended to be exceptions. In popular culture, yoga went on its merry way, oblivious to the conclusion of science, believing deeply in its aerobic powers, often selling itself as superior to sports and exercise as the one and only way to attain that most fashionable of goals—ultimate fitness.

  Yoga Journal continued its claims, hailing vigorous Hatha in 2008 as “a good cardio workout.”

  The vibrant cover of Yoga for Dummies publicized its two authors as holding doctoral degrees—the ultimate academic credential. Their experience seemed to magnify their authority. The cover identified one man as the “author of more than 40 books,” and the other as an “internationally renowned Yoga teacher.” In the book’s second edition, published in early 2010, the two authorities hailed the Sun Salutation for its “aerobic benefits.” More generally, they assured readers, the newer, more vigorous formulations of the ancient discipline let practitioners “work up a sweat” to achieve “aerobic-type” workouts.

  Even The New York Times lost its bearings. One of its companies, About.com, addressed a frequent question of readers, “Does Yoga Keep You Fit?” Yes, came the unequivocal answer. Ann Pizer, the website’s “Yoga Guide,” said recent science had revealed that students doing yoga more than twice a week “need not supplement their fitness regimes with other types of exercise in order to stay very physically fit.” She cited the original Yoga Journal article, the one that had turned the Davis study into a publicist’s dream come true.

  An indication of the fog’s deep penetration was how it crept into the pages of Hotel Management and Operations—an industry guide in its fifth edition. In 2010, it advised readers that vigorous styles such as Ashtanga were ideal for getting a “cardio workout.” The language wasn’t as strong as Beth Shaw’s “tough cardiovascular workout.” But it nonetheless put the practice right up there with the sweaty rigors of fast treadmills.

  The Davis and Yoga Journal articles kept getting cited, their claims immortalized on the Internet. The Huffington Post ran a link to Yoga Journal’s glowing tribute.

  The aerobic mythology sped across cyberspace until it found its way to HealthCentral.com, a flourishing commercial site that sells drugs and gives away medical advice. The site claims more than seventeen million readers a month and, on its home page, proudly declares that it features material from Harvard Health Publications, the arm of the Harvard Medical School that seeks to publicize the most authoritative health information. The site’s reference to Harvard included a picture of the school’s crest—a shield bearing three open books, their pages spelling out veritas—”truth” in Latin.

  “Does Yoga Provide Enough of a Cardio Workout?” HealthCentral .com asked its readers in 2010.

  The answer came from never-ne
ver land, despite the implication that the Harvard Medical School had somehow been involved in producing or vetting the information. It came from a place where the ancient practice had somehow morphed into a modern fitness machine.

  “Rest assured,” the site told its readers. “Yoga is all you need.”

  In recent years, many people have learned to ignore the exaggerated claims and the unabashed gurus (with or without fleets of Rolls-Royces). They lift weights to build muscles and run to challenge their hearts, even while pursuing yoga for flexibility and its other rewards. They are known as cross trainers. Their diverse workouts complement one another to produce a balance of benefits.

  Cross training has no gurus, no schools, no fees, and no advocacy groups. Even so, it has a growing number of adherents, including top athletes. For instance, Alan Jaeger, a baseball pro with a passion for yoga, runs a school in Los Angeles for big-league pitchers. His stars run, stretch, meditate, listen to music, do yoga poses, and meditate again—doing that kind of routine for hours before getting around to throwing a ball.

  The popularity of cross training serves as an instructive counterpoint to yoga’s overstated fitness claims. It speaks to the wisdom of people who pay close attention to what their bodies tell them tell them—and to the recommendations of public health officials.

  The guidelines for aerobic exercise developed slowly over the course of the twentieth century, as we have seen. Ultimately, the enterprise drew on the work of hundreds of scientists. A less conspicuous effort got under way during the same period. It focused not on the straightforward goal of quantifying oxygen uptake and determining its role in physical fitness but on the more difficult and amorphous problem of understanding how changing situations can shape human emotion.

  By nature, the mood question was far more challenging than studying the ups and downs of VO2 max. An added complication was that the investigation of human feeling had less political traction because it involved fewer scientists, received less funding, and had less institutional support than was the case with research into sports and physical training. The pool of candidates shrank further still when the focus was on such curiosities as yoga. The discoveries in that case could be quite serendipitous in nature, as with the Duke investigators.

  Scattered groups of scientists nonetheless made notable progress in the course of the twentieth century. In recent years, their work has become more abundant and substantial. The field—after an early history of false starts and digressions—now appears to be coming into its own.

  The trend is significant. In the end, it may elucidate one of yoga’s most important benefits.

  III

  MOODS

  Sat Bir Khalsa chatted amiably as we walked down the street. His beard was long and gray, his turban white, and his bracelet made of steel—all signs of his Sikh religion. He was not, however, Indian. Born in Toronto of European stock, he had converted to Sikhism decades ago upon taking up Kundalini Yoga, an energetic form that emphasizes rapid breathing and deep meditation.

  No one on Longwood Avenue seemed to give the turbaned Sikh a second look. Boston that spring day was gorgeous. An early shower had scrubbed the air, leaving it awash in sunlight. Flowers and trees were blooming. Men and women were shedding their coats. People fairly hummed along the sidewalks.

  We had just eaten lunch at Bertucci’s, a bustling restaurant where Khalsa had finished his meal with bomba—“the bomb” in Italian. The dessert consisted of balls of vanilla and chocolate gelato dipped in chocolate and covered with almonds, whipped cream, and chocolate sauce. I could see why his kids loved the place.

  Maybe it was the sugar high, or the beautiful day, or the yoga. Whatever the cause, the air fairly pulsed as Khalsa—a faculty member at the Harvard Medical School and one of the world’s leading authorities on the science of yoga—laid out his findings and ambitions. The friendly man of fifty-six turned out to have a lot.

  At Harvard, Khalsa had pursued a bold program of research that explored how yoga can soothe physically and emotionally. His focus was practical—and structured that way deliberately to demonstrate yoga’s social value. He had examined how its powers of unwinding can promote sleep and ease performance anxiety among musicians, and was now organizing a study to see if its calming influence could help high school students better fight the blues and everyday stress. Khalsa had ten yoga investigations in various stages of development.

  With energy and articulate zeal, he described his research as a way to help yoga break from its fringy past and go mainstream.

  “What ever happened to mental hygiene?” he asked rhetorically. “It doesn’t exist—and never did. When you went through high school, you were never taught how to deal with stress, how to deal with trauma, how to deal with tension and anxiety—with the whole list of mood impairments. There’s no preventive maintenance. We know how to prevent cavities. But we don’t teach children how to be resilient, how to cope with stress on a daily basis.

  “There’s a disconnect,” he continued. “We’ve done dental hygiene but not mental hygiene. So the question is, ‘How do we go from where we are now to where we need to be?’”

  Khalsa argued that the only way to convince people about the value of yoga and establish a social consensus that encouraged wide practice was to conduct a thorough program of scientific research. He added that recommendations for regular toothbrushing had started that way and illustrated the potential value of good yoga studies.

  “That’s my mission in life,” Khalsa told me.

  This chapter examines not only Khalsa’s research but many inquiries into how yoga can lift moods and refresh the human spirit. It starts with the earliest research and ends with the most recent. The arc of the narrative is really a detective story. The studies began with the muscles (and how yoga can relax them), went on to study the blood (and how yoga breathing can reset its chemical balance), and eventually zeroed in on the subtleties of the nervous system (and how yoga poses can fine-tune its status). The discipline was found to lift and lower not only emotions but also their underlying constituents—the metabolism and the nervous system.

  The mood benefits detailed here are very real, unlike some of the aerobic claims of the last chapter. But the field also has its popular myths. They tend to be outright errors, probably rooted in ignorance rather than subtle shadings of the truth done with profit in mind.

  Psychologists tell us that a fundamental building block of emotional life is strong feeling, such as fury or affection. By definition, moods are considered less intense, more general, longer lasting, and less likely to arise from a particular stimulus. They are seen as drawn-out emotions. For instance, joy over a period of time produces a happy mood. Sadness over time results in depression. Unlike sharp feelings such as rage or surprise, moods tend to last for hours and days, if not weeks. If intense, they can color our life perceptions—at times dramatically.

  Moods are central to meaning in life and thus, in the judgment of psychologists, more important than money, status, and even personal relationships because they affect the happiness quotient that we assign to life activities. As the saying goes, a rich man in a bad mood can feel destitute, and a poor man in a good mood rich beyond words. To a surprising degree, moods define our being.

  It turns out that the word arose in the earliest days of the English language and that its first definitions resonate with existential import. “Mood” was originally a synonym for “mind.” In Old English, the word mod meant “heart,” “spirit,” or “courage.”

  An intriguing question that investigators have yet to address is whether yoga can change an individual’s pattern of moods—in other words, a person’s core emotional outlook. Can the regular practice of Sun Salutations produce a sunny disposition? Does yoga bring about what might be considered characteristic states of affability?

  Many people have looked to their own experience on such matters and found that, overall, yoga lifts their emotional life. Significantly, the vast majority are women. />
  The conventional wisdom is that episodes of major depression strike women twice as frequently as men. The drug evidence is stark. A survey found women nearly three times as likely as men to take antidepressants—with usage as high as one in every four or five women.

  If those characterizations are right, yoga should resonate strongly with women as a way of fighting the blues. I personally saw evidence of that attraction. In the early winter of 2010, I joined dozens of women (and a few guys) who had gathered to learn about using the discipline as a means of emotional uplift.

  “It really saved my life,” Amy Weintraub told us during her introductory talk. “I wouldn’t be here.” It was Friday night at Kripalu, the yoga center in the Berkshires of western Massachusetts. Weintraub, author of Yoga for Depression, was leading a weekend seminar on mood management.

  She came to her calling after a life of crippling dejection and numbness. “I moved as through a fog,” she recalled in her book. “I lost keys, gloves, and once, even my car.” Antidepressants did little. Then she found yoga. The fog lifted. In a year, she was off drugs and soon became a yoga instructor. Her rebirth came with deep feelings of emotional strength.